After dissolution in an organic solvent medium certain organic compounds constitute a working solution. The working solution containing anthraquinone is reduced to the anthrahydroquinone state by catalytic hydrogenation; and the anthrahydroquinone is then oxidized to the anthraquinone hydroperoxide state. This latter, still dissolved in the solvent medium, is subjected to a treatment with water. It is thus decomposed into hydrogen peroxide which dissolves in the water, and into anthraquinone which remains in solution in the organic solvent medium and is sent to the reduction stage.
The organic solvent used in the process should be able to dissolve both the oxidized form (anthraquinone) and reduced form (anthrahydroquinone). Since solvents that can be used and dissolve the two forms satisfactorily are rare, most often a mixture of constituents is used.
The solvents used in the anthraquinone process are usually two-constituent systems in which a solvent of the hydrocarbon type dissolves the quinone and a polar type solvent dissolves the hydroquinone.
The solvent systems used should be good solvents of both the quinone and hydroquinone forms, while being barely sensitive to degradation during the hydrogenation and oxidation phases. Further, they should have a slight solubility in water and aqueous solutions of hydrogen peroxide; and their density should be such that extraction of the hydrogen peroxide can be performed by simple separation of the aqueous and organic phases. Further, these solvent systems should also have a slight volatility associated with a high distribution coefficient of the hydrogen peroxide.
German DAS 1,945,750 proposed tert-butylbenzene as a solvent for quinone, which solvent is resistant to oxidation without notable degradation at 140.degree. C. during several hours.
French patent No. 2,244,709 presented amides of carboxylic acids of the formula ##STR1## in which R.sub.1, R.sub.2, and R.sub.3 are alkyl groups having 1 to 8 carbon atoms, as solvents of the anthraquinones used in the production of hydrogen peroxide, in particular in the form of mixtures with other solvents; but it has been found that the polar solvents are unstable because not resistant enough to oxidation.
Consequently, it appeared necessary to search for solvents exhibiting all the qualities associated with a very high resistance to oxidation and making possible the production of hydrogen peroxide with high yields.